dma-debug: add function to dump dma mappings

This adds a function to dump the DMA mappings that the debugging code is
aware of -- either for a single device, or for _all_ devices.

This can be useful for debugging -- sticking a call to it in the DMA
page fault handler, for example, to see if the faulting address _should_
be mapped or not, and hence work out whether it's IOMMU bugs we're
seeing, or driver bugs.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

2 files changed, 36 insertions, 0 deletions

diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index 4985c6c5237e..46a11c10da04 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -76,6 +76,8 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,
                                          struct scatterlist *sg,
                                          int nelems, int direction);
 
+extern void debug_dma_dump_mappings(struct device *dev);
+
 #else /* CONFIG_DMA_API_DEBUG */
 
 static inline void dma_debug_init(u32 num_entries)
@@ -156,6 +158,10 @@ static inline void debug_dma_sync_sg_for_device(struct device *dev,
 {
 }
 
+static inline void debug_dma_dump_mappings(struct device *dev)
+{
+}
+
 #endif /* CONFIG_DMA_API_DEBUG */
 
 #endif /* __DMA_DEBUG_H */
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 9d11e89c2ee2..91ed1dfdbaac 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -194,6 +194,36 @@ static void hash_bucket_del(struct dma_debug_entry *entry)
 }
 
 /*
+ * Dump mapping entries for debugging purposes
+ */
+void debug_dma_dump_mappings(struct device *dev)
+{
+        int idx;
+
+        for (idx = 0; idx < HASH_SIZE; idx++) {
+                struct hash_bucket *bucket = &dma_entry_hash[idx];
+                struct dma_debug_entry *entry;
+                unsigned long flags;
+
+                spin_lock_irqsave(&bucket->lock, flags);
+
+                list_for_each_entry(entry, &bucket->list, list) {
+                        if (!dev || dev == entry->dev) {
+                                dev_info(entry->dev,
+                                         "%s idx %d P=%Lx D=%Lx L=%Lx %s\n",
+                                         type2name[entry->type], idx,
+                                         (unsigned long long)entry->paddr,
+                                         entry->dev_addr, entry->size,
+                                         dir2name[entry->direction]);
+                        }
+                }
+
+                spin_unlock_irqrestore(&bucket->lock, flags);
+        }
+}
+EXPORT_SYMBOL(debug_dma_dump_mappings);
+
+/*
  * Wrapper function for adding an entry to the hash.
  * This function takes care of locking itself.
  */